Illuminated signs are widely used by businesses and other entities to indicate the location of a place of business or to display information to the public in a manner that may be readily seen at nighttime or during other periods of low light. While many forms of illuminated signs are known, one popular and economic method of providing an illuminated sign involves the use of high intensity discharge (HID) lamps in conjunction with transparent or translucent sign panels having visible indicia mounted or otherwise disposed on the surface of the panels. The HID lamp is positioned behind the sign panel and light is transmitted through the panel to illuminate the sign.
HID lamps are known in the art and operate by creating an arc between metal electrodes to produce high levels of intense light from a relatively small source. HID lamps are relatively energy efficient and provide long service life. Similar to fluorescent lamps, HID lamps require a ballast to aid in starting and maintaining operation of the lit lamp. Because HID lamps require high-voltage electricity and emit heat and ultraviolet radiation, manufacture and use of HID illuminated signs are covered by various codes, such as the National Electric Code, and standards, such as those developed by organizations such as Underwriters Laboratories, Inc. (UL®).
To fabricate an HID illuminated sign, a manufacturer typically obtains lamp components, such as HID lamp sockets and ballasts, and integrates the individual components into a sign support structure according to guidelines such as those established by the UL® standards. Accordingly, fabrication of each illuminated sign essentially involves assembling the HID lamp components from scratch, largely because the UL® requirements have made it difficult to integrate the components into a modular fixture which may be used for all sign configurations. In particular, integrating the components into a single fixture makes it difficult to dissipate heat generated by the HID lamp and the ballast in accordance with UL® standards. To better control the heat, transformers are often potted in an insulative material, such as asphalt, and therefore the assemblies are very heavy.
One commercially available lighting fixture is a perimeter lighting system that is configured to be mounted within the interior of an illuminated sign at locations around the peripheral edge of the sign. Accordingly, one drawback of this lighting fixture is that the light is concentrated toward the outer periphery of the sign and therefore does not uniformly light interior portions of the sign. The fixture requires a lens to help direct light toward the center of the sign and is also relatively heavy and expensive. Other conventional HID luminaires are generally unacceptable for illuminating interiorly lit signs because such luminaires are configured to provide highly directional lighting, whereas the objective of illuminated signs is to provide as much light as possible in every direction
A need therefore exists for a lightweight, economical fixture for mounting HID lamps which is convenient for use in illuminated signs.